This invention relates to a laryngeal mask airway device (LMA) and to a method suitable for making such a device.

The LMA is a well known device that is useful for establishing airways in unconscious patients. LMAs have been in use for many years and offer an alternative to the older, even better known, endotracheal tube. For at least seventy years, endotracheal tubes comprising a long slender tube with an inflatable balloon disposed at the tube's distal end have been used for establishing airways in unconscious patients. In operation, the endotracheal tube's distal end is inserted through the mouth of the patient, past the patient's laryngeal inlet (or glottic opening), and into the patient's trachea. Once so positioned, the balloon is inflated so as to form a seal with the interior lining of the trachea. After this seal is established, positive pressure may be applied to the tube's proximal end to ventilate the patient's lungs. Also, the seal between the balloon and the inner lining of the trachea protects the lungs from aspiration (e. g. the seal prevents material regurgitated from the stomach from being aspirated into the patient's lungs).

Although they have been enormously successful, endotracheal tubes suffer from several major disadvantages. The principal disadvantage of the endotracheal tube relates to the difficulty of properly inserting the tube.

Inserting an endotracheal tube into a patient is a procedure that requires a high degree of skill. Also, even for skilled practitioners, insertion of an endotracheal tube is sometimes difficult or not possible. In many instances, the difficulty of inserting endotracheal tubes has tragically led to the death of a patient because it was not possible to establish an airway in the patient with sufficient rapidity.

In addition to this principal disadvantage, there are also other disadvantages associated with endotracheal tubes. For example, intubation with an endotracheal tube often causes patients to suffer from severe "sore throats". The "sore throat" is principally caused by friction between the tube and the notch between the patient's arytenoid cartilages. Another disadvantage is that patients cannot cough effectively while intubated with an endotracheal tube. Yet another problem with endotracheal tubes relates to the manner in which they are inserted. Inserting an endotracheal tube normally requires manipulations of the patient's head and neck and further requires the patient's jaw to be forcibly opened widely. These necessary manipulations make it difficult, or undesirable, to insert an endotracheal tube into a patient who may be suffering from a neck injury. Still another disadvantage is that endotracheal tubes provide an airway that is relatively small or narrow. The size of the airway must be relatively narrow because the distal end of the tube must be sufficiently small to fit into the trachea.

In contrast to the endotracheal tube, it is relatively easy to insert an LMA into a patient and thereby establish an airway. Also, the LMA is a "forgiving" device in that even if it is inserted improperly, it still tends to establish an airway. Accordingly, the LMA is often thought of as a "life saving" device. Also, the LMA may be inserted with only relatively minor manipulations of the patient's head, neck, and jaw. Further, the LMA provides for ventilation of the patient's lungs without requiring contact with the sensitive inner lining of the trachea and the size of the airway established with an LMA is typically significantly larger than the size of the airway established with an endotracheal tube. Also, the LMA does not interfere with coughing to the same extent as endotracheal tubes. Largely due to these advantages, the LMA has enjoyed increasing popularity in recent years.

Figure 1 shows a perspective view of a prior art LMA 100 and Figure 2 illustrates an LMA 100 that has been inserted into a patient. LMAs such as LMA 100 are described for example in US 4,509,514. LMA 100 includes an airway tube 1 10 and a mask 130. Airway tube 110 extends from a proximal end 1 12 to a distal end 1 14 and mask 130 is coupled to the tube's distal end 114. Mask 130 includes a proximal end 132 and a generally elliptical inflatable cuff 134. Mask 130 also defines a central passageway extending from proximal end 132 to an open end 136 of cuff 134. The distal end 114 of tube 1 10 is telescopically fit into the proximal end 132 of mask 130, and LMA 100 provides a continuous airway extending from proximal end 1 12 of tube 1 10 to the open end 136 of cuff 134. LMA 100 also includes an inflation tube 138 for selectively inflating or deflating cuff 134. In operation, the cuff 134 is deflated, and then the mask is inserted through the patient's mouth into the patient's pharynx. The mask is preferably positioned so that a distal end 139 of cuff 134 rests against the patient's normally closed oesophagus and so that the open end 136 of the cuff 134 is aligned with the entryway of the patient's trachea (i. e., the patient's glottic opening). After the mask is so positioned, the cuff is inflated thereby forming a seal around the patient's glottic opening and this establishes a sealed airway extending from the proximal end 112 of the tube 110 to the patient's trachea.

When LMA 100 is in the fully inserted configuration, LMA 100 advantageously does not contact the interior lining of the trachea. Rather, the seal is established by contact between the tissues surrounding the patient's laryngeal inlet and the inflatable cuff 134. Unlike the delicate interior lining of the trachea, the tissues at the laryngeal inlet are accustomed to contact with foreign matter. For example, during the act of swallowing food, the food is normally squeezed against these tissues on its way to the oesophagus. These tissues are accordingly less sensitive and less susceptible to being damaged by contact with the inflatable cuff.

The airway tube 110 of LMA 100 may take the form of a cylinder of flexible plastic or may take the form of a rigid, anatomically curved tube. Depending on the materials used to make a particular LMA product, an LMA may be re-usable following sterilisation. For example, the LMA Classic™, LMA ProSeal™, LMA Fastrach™, LMA Flexible™ and LMA CTrach™ (all sold by LMA North America, Inc) are guaranteed to survive forty sterilizations, and in practice these devices may generally be sterilized (and reused) more than forty times before becoming too worn for reuse.

Figure 3 shows a dorsal view of an alternative prior art airway device, known as an NLMA 200. NLMAs such as NLMA 200 are described for example in WO 04/016308. NLMA 200 includes an airway tube 210 and a mask 230. Airway tube 210 is housed within a buccal cavity stabiliser 220 and extends from a proximal end 212 to a distal end 214. Mask 230 includes a generally elliptical non-inflatable cuff 234 on its laryngeal side, which cuff 234 is coupled to the tube's distal end 214. A central passageway extends through the cuff 234 to provide a continuous airway extending from proximal end 212 of tube 210 to the open end 236 of cuff 234. NLMA 200 does not include an inflation tube. When inserted into a patient an NLMA 200 will closely resemble an LMA 100 that has been inserted into a patient, except for the absence of an inflation tube. As with an LMA 100, in operation, the mask 230 of the NLMA 200 is inserted through the patient's mouth into the patient's pharynx and positioned in the same way around the patient's glottic opening. The NLMA 200 is made from two types of a gel-like thermoplastic material, styrene ethylene butadiene styrene (SEBS). The buccal cavity stabiliser 220 and the pharyngeal side of the mask 230 are made from a firmer type of SEBS, whilst the cuff 234 located on the laryngeal side of the mask 230 is made from a softer type of SEBS. As SEBS is a flexible material, the NLMA 200 curves within a patient's upper airway as it is inserted. Once the NLMA has been inserted and correctly positioned, the non-infJatable cuff 234 envelops the laryngeal inlet to establish a sealed airway extending from the proximal end 212 of the airway tube 210 to the patient's trachea. NLMAs are only suitable for a single-use because SEBS is not suitable for sterilisation and re-use.

A rigid airway rube can be gripped by a user, which helps a user guide an LMA incorporating such a tube into a patient, thereby aiding insertion. However, LMAs with rigid airway tubes are not suited to all potential applications, for example an application in which the patient's head needs to be moved following insertion of the device. LMAs with flexible airway tubes are particularly suited to certain applications, e.g. nasal surgery when it is desirable that the proximal end of the airway tube be positioned away from the surgical site and can reliably negotiate the insertion path of an LMA to the fully inserted configuration within a patient without causing damage to the patient's anatomy. However, LMAs with flexible airway tubes can be difficult to insert into a patient and difficult to properly position within a patient. Therefore, it would be advantageous to develop an LMA with a relatively flexible airway tube.

According to a first aspect, the invention provides an LMA for insertion into a patient to provide an airway passage to the patient's glottic opening, said device comprising an airway tube, a mask attached to the airway tube, the mask comprising a body having a distal end and a proximal end, a peripheral cuff, and defining an outlet for gas, the mask being connected to the airway tube for gaseous communication between the tube and the mask, the airway tube comprising a relatively more rigid thermoplastic skeleton and at least one layer of a relatively more flexible thermoset material. The relative quantities of the rigid thermoplastic and flexible thermoset may be adjusted to vary the flexural rigidity of the airway tube. Preferably, the at least one layer of a relatively more flexible thermoset material forms an outer layer, however, airway tube may comprise a flexible thermoset inner layer in addition to the relatively more flexible thermoset outer layer, or a single layer may be formed around the relatively more rigid thermoplastic skeleton.

The skeleton of the airway tube may be considered as having three sections, a proximal portion, a central portion and a distal portion. The proximal portion is the part which, in use, may be coupled to air supply means and therefore the cross-section of the proximal portion of the skeleton may be an enclosed perimeter to allow the rigid thermoplastic perimeter to be readily connected to the air supply means. The distal portion forms part of the mask of the laryngeal mask airway device and, once a cuff has been attached, enables the establishment of a sealed airway extending from the proximal end of the airway tube to the patient's trachea. In cross-section the distal portion of the skeleton may be an enclosed perimeter to allow the rigid thermoplastic perimeter to be readily connected to the cuff. However, the central portion need not be connected to another part of the device or to a separate device, therefore a cross-section of the central portion of the skeleton may not be an enclosed perimeter. The at least one space formed within the central portion of the skeleton forms at least one window. The flexible thermoset layer forms a surface that covers any windows within the skeleton to form an airtight airway tube.

The skeleton, which has a left side and a right side, a dorsal face and a ventral face, may have at least one rib linking the left side to the right side to form more than one window on the dorsal face or the ventral face of the skeleton within its central portion. Alternatively, or additionally, the skeleton may have at least one rib linking the dorsal face of the central portion to the ventral face of the central portion such that more than window is formed on at least one of the sides of the skeleton within its central portion. Ribs provide flexural rigidity and can as a guide for an endotracheal tube inserted through a laryngeal mask device. US 5,303,697 and US 6,079,409 describe examples of prior art devices that may be referred to as "intubating laryngeal mask airway devices", i.e. devices designed to facilitate insertion of an endotracheal tube. After an intubating laryngeal mask airway device is in a patient in the fully inserted configuration, the device can act as a guide for a subsequently inserted endotracheal tube. Use of the laryngeal mask airway device in this fashion facilitates what is commonly known as "blind insertion" of the endotracheal tube. Only minor movements of the patient's head, neck and jaw are required to insert the intubating laryngeal mask airway device, and once the device has been located in the patient, the endotracheal tube may be inserted with virtually no additional movements of the patient. This contrasts with the relatively large motions of the patient's head, neck and jaw that would be required if the endotracheal tube were inserted without the assistance of the intubating laryngeal mask airway device. Furthermore, these devices permit single-handed insertion from any user position without moving the head and neck of the patient from a neutral position, and can also be put in place without inserting fingers in the patient's mouth. Finally, it is believed that they are unique in being devices which are airway devices in their own right, enabling ventilatory control and patient oxygenation to be continuous during intubation attempts, thereby lessening the likelihood of desaturation. Artificial airway devices of this type are exemplified by the disclosures of US 4,509,514; US 5,249, 571 ; US 5,282,464; US 5,297,547; US 5,303,697; and GB 2,205,499. Such devices with additional provision for gastric-discharge drainage are exemplified by US 4,995,388 (Figs. 7 to 10); US 5,241 ,956; and US 5,355,879.

The cuff of an LMA according to the present invention may be inflatable or non-inflatable. Inflatable cuffs require the use of an inflation tube and may comprise a thermoset material, such as polyvinyl chloride (PVC). Non-inflatable cuffs may comprise a thermoplastic or a foam material.

It has been found that a ventral displacement of the distal end of the mask makes insertion of the device easier because the tip is presented at an optimum angle as it "turns the corner" in the insertion path of a patient's airway. Therefore, in one embodiment of a laryngeal mask airway device according to the present invention, the distal end of the mask is ventrally displaced, relative to the proximal end. If the mask is ventrally displaced, it is preferred that the extent of displacement is from about 5 mm to about 20 mm, and it is most preferred that the extent of distal displacement is about 10 mm. The ventral displacement may also be expressed in degrees, so that the extent of displacement may be approximately 10 degrees. This has been found to be the optimum range, as it suits the anatomy of most patients.

In one embodiment the mask body describes a substantially convex curve, from the proximal end of the mask to the distal end of the mask. Optionally, the dorsal face of the mask body is substantially smooth and has a convex curvature across its width. The dorsal face of the airway tube corresponds in curvature to the curvature across the dorsal face of the mask body, i.e. across from the left side to the right side of the dorsal face of the airway tube. These features aid in the insertion of the claimed device and increase patient comfort. Additionally, minimising the device's dorsal to ventral dimension further aids insertion. In another embodiment, the device further comprises means to prevent occlusion of the outlet by the patient's anatomy, the means comprising a support, and at least one conduit to allow gas to flow out of the outlet past the support. If there are a plurality of conduits, the conduits may be arranged about the support, e.g. two conduits may be arranged either side of the support.

Usually, the support is disposed on the ventral face of the mask, in front of the at least one outlet in the path of gas flow. Preferably the outlet includes a floor, the support providing an occluding anatomical structure above the level of the floor, to allow gas to flow therebelow. The support may be provided upon a substantially centrally disposed, longitudinal upstand, extending from in front of the outlet towards the distal end, which raises the upper surface of the support to above the level of the ventral face of the mask.

The at least one conduit may include a floor, the floor being defined by a part of the ventral face of the mask body. The at least one conduit may be defined by side walls, at least one side wall being defined by a part of the support. The at least one conduit may have a substantially circular cross-section. The side walls may include laterally extending webs, to partially close over the at least one conduit. The webs may include upper surfaces disposed at the same level as the upper surface of the support, to prevent entry of an occluding structure into the at least one conduit.

In one embodiment the laryngeal mask airway device comprises an oesophageal drain, the drain comprising a conduit extending from an inlet at the distal end of the mask body to an outlet disposed to be outside of the patient when the device is in a patient in the fully inserted configuration, the drain conduit including a mask section and an airway tube section, wherein the drain conduit mask section is formed integrally in the material of the body. The oesophageal drain tube may be formed on and extending from the ventral side of the mask body, in order to maintain a smooth profile on the dorsal side, to make insertion easier. Preferably the drain conduit extends substantially centrally from the distal end to the proximal end of the mask body, so that a straight and short flow path for liquids and solids is provided.

Optionally, the drain conduit can include an extension part which extends past the distal extent of the mask body. The extension part may be enclosed by, and open out of an integrally formed pocket, and the pocket preferably extends from the material of the inlet. The pocket is preferably inflatable, and most preferably is inflated by gas from the cuff. The pocket and cuff can be sealed together, there being an access way for gas from the cuff to the pocket, and the access way can conveniently be provided by a pinch-off of the cuff.

The extension part may include means to prevent it collapsing under increased air pressure in the pocket. The prevention means may comprise at least one support web formed integrally with the extension part, and the or each support web may extend from the extension part, substantially perpendicular thereto.

In embodiments including means to prevent occlusion of the outlet by the patient's anatomy, the support may be formed from an outer surface of an oesophageal drain tube. Alternatively, the support may be integrally formed in the material of the mask body or may be integrally formed with the at least one layer of a relatively more flexible thermoset material.

Suitable techniques for use in manufacturing LMAs according to the present invention include injection moulding to make the skeleton and over moulding to make the at least one layer of a relatively more flexible thermoset material. Of course, additional process steps may be included in manufacturing the skeleton and/or at least one layer of a relatively more flexible thermoset material.

According to a second aspect, the invention provides a method of constructing an LMA as described above, said method comprising:

a) , providing a thermoplastic skeleton of an airway tube; and

b) . overmoulding a first layer of a relatively more flexible thermoset material onto the skeleton to form an airway tube.

The method may include an additional step:

c) . overmoulding a second layer of a relatively more flexible thermoset material onto the skeleton. In one embodiment, the method further comprises overmoulding a mask body onto the airway tube, and attaching a cuff to said mask body. In embodiments including a mask body being overmoulded onto the distal end of the airway tube, the method may also include the step of providing an airway tube including attachment surfaces to assist in the provision of a secure attachment. The attachment surfaces may take the form of flared portions and/or through holes in the surface of the distal end of the airway tube to allow an over moulded mask body to lock onto the distal end of the airway tube.

In embodiments including inflatable cuffs, the method may further comprise the step of forming the cuff by blow-moulding prior to attaching it to the mask, attaching it to the mask as a gas-tight member, then removing a pinch-off after attachment.

In embodiments including an oesophageal drain tube, the method may further comprise the step of moulding the mask body to include an integral oesophageal drain tube, and attaching the integrally moulded drain tube to a drain tube of the airway. Additionally, the method may include the step of integrally moulding a cuff to the circumference of the drain tube opening. Suitable materials for use in construsting LMAs according to the present invention include nylon (such as Grilamid 60 available from EMS Grivory) and polysulfone to make the skeleton and liquid silicon rubber (such as the self-adhesive Elastosil LR 3071 available from Wacker-Chemie) to make the at least one layer of a relatively more flexible thermoset material. The cuff may be made from PVC. Of course, additional components may be included in manufacturing the skeleton and/or at least one layer of a relatively more flexible thermoset material.

In embodiments including an overmoulded mask body, the mask body may be made from a combination of PVC and polyurethane (PU). This material is relatively more flexible than the rigid thermoplastic skeleton and relatively more rigid than the flexible thermoset used to make the at least one layer of a relatively more flexible thermoset material.

Re-usable LMAs should be made from materials suited to cleaning, e.g. highly resistant to steam autoclaving and other medical device cleaning equipment and chemicals. Grilamid 60 and Elastosil LR 3071 are such materials.

Brief Description of the Figures

For a fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken in connection with the accompanying drawings in which the same reference numerals are used to indicate the same or similar parts wherein:

Figure 1 shows a perspective view of a prior art LMA;

Figure 2 shows a prior art LMA inserted into a patient in the fully inserted configuration; Figure 3 shows a dorsal view of a prior art NLMA;

Figure 4 shows a perspective view of one embodiment of an LMA according to the present invention;

Figure 5 shows a side view of the LMA of Figure 4;

Figure 6 shows an enlarged view of the ventral face of the mask of the LMA of Figures 4 and 5;

Figure 7 shows a perspective view of one embodiment of the skeleton of an airway tube according to the present invention; Figure 8 shows a dorsal view of one embodiment of the skeleton of an airway tube according to the present invention;

Figure 9 shows a ventral view of one embodiment of the skeleton of an airway tube according to the present invention; and

Figure 10 shows a method of making an LMA according to the present invention.

Detailed Description of the Preferred Embodiments

Figure 4 shows a perspective view of one embodiment of an LMA 400 constructed according to the invention. LMA 400 has an airway tube 410 and a mask 430 attached to the airway tube 400. The mask 430 has a mask body 431, having a proximal end 432 and a distal end 433, and a peripheral cuff 434, which defines an outlet for gas 440. The cuff 434 is shown in an inflated condition.

In this embodiment, the LMA 400 further comprises an oesophageal drain 450 formed on and extending from the ventral face of the mask 435, in order to maintain a smooth profile on the dorsal face 437, which makes insertion easier. The drain comprises a drain conduit extending from an inlet 452 at the distal end of the mask 433 to an outlet 454 disposed to the outside of the patient when the LMA 400 is in a patient in the fully inserted configuration. The drain conduit includes a mask section 456 and an airway tube section 458. The drain conduit mask section 456 forms an integral part of the mask 430.

In this embodiment, the airway tube 410 does not have a circular cross-section, as in many prior devices, but instead is compressed in the dorsal/ventral direction. The compressed cross-section of the airway tube 410 assists with the correct insertion of the device, helps prevent kinking, and increases patient comfort as the shape of the airway tube more closely mimics the shape of the patient's airway. In this embodiment both the left side and the right side of the airway tube 410 include a groove or channel 416 extending for most of the tube's length from its proximal end 412 to its distal end 414. These grooves or channels 416 further assist in preventing crushing or kinking of the airway tube 410. Internally the grooves or channels 41 form ridges along the inner surfaces of the sides of the airway tube 410. The proximal end 412 of the airway tube 410 is provided with a connector 460, for connection of the LMA 400 to a gas supply and drain (not shown). The connector 460 comprises a connector body 462 with an optional bite block 464. The connector 460 may be integrally formed with the airway tube 410, or the connector body 462 and bite block 464 may correspond in shape and dimension with the internal shape of the proximal end 412 of the airway tube 410 such that they fit inside it. The connector body 462 has a tab 466, which may be used to fix the LMA 400 to a patient using adhesive tape when the LMA 400 is in a patient in the fully inserted configuration. The connector body has major and minor bores 468, 469. The airway tube section of the oesophageal drain tube 458 extends into and through minor bore 469, such that the airway tube 410 and the oesophageal drain 450 are separated from one another.

Figure 5 shows a side view of the LMA 400. In the embodiment depicted in Figures 4 and 5, the peripheral cuff 434 is made from blow moulded PVC and takes the form of a generally elliptical inflatable ring. The cuff 434 is attached to the mask body 431, often referred to as a back plate, to form the mask 430. The mask body 431 is curved, from the proximal end of the mask 432 to the distal end of the mask 433, thereby ventrally displacing the distal end of the mask 433 relative to the proximal end 432. (The extent of displacement is shown schematically at X in Figure 5.) The dorsal face of the mask body 437 is substantially smooth and has a convex curvature across its width. The dorsal face of the airway tube 415 corresponds in curvature to the curvature across the dorsal face of the mask body 437, i.e. across from the left side to the right side of the dorsal face of the airway tube 415.

Figure 6 shows an enlarged view of the ventral face of the mask 430 of the LMA 400. The conduit of the oesophageal drain 450 passes through the centre of the mask body 431 to drain outlet 454. The combination of the centrally located drain conduit 454 and the minor gas conduits 442 located either side of the drain conduit 454 assist in solving the problem of occlusion of the airway by parts of the patient's anatomy. The minor gas conduits 442 can be thought of as "nostrils" through which gas may continue to pass into the patient even if the main outlet 440 becomes occluded by, for example the patient's epiglottis, because the epiglottis will rest upon the support provided by the upper surface of the conduit of the oesophageal drain 450. In turn, the support does not block the outlet 440 because it is positioned in front of the outlet 440 and above the level of the floor of the outlet 440.

The support provided by the upper surface of the conduit of the oesophageal drain 450 is on a a level approximately equal to the level of the webs 446, 448. The webs 446, 448 extend laterally towards each other but do not meet. By extending across the top of the minor gas conduits 442 the webs 446, 448 form a partial closure over the minor gas conduits 442 and assist in preventing structures such as the epiglottis from falling into and blocking the minor gas conduits 442. The floors of the the minor gas conduits 442 curve gently upwards as they extend towards the distal end of the mask 433 until they terminate at a level approximately equal to the level of the webs 446, 448.

The webs 446, 448 also help to make the mask body 431 more resistant to lateral compression. Although in this embodiment it is the upper surface of the conduit of the oesophageal drain 450 that provides a support to prevent occlusion of the outlet 440 by the patient's anatomy, in LMAs without an oesophageal drain 450, a separate solid septum could be formed integrally with the mask body 431 to perform the same function.

Figures 7 to 9 show various views of the skeleton 470 of an airway tube according to the present invention. As described above, the skeleton 470 is made of a relatively more rigid thermoplastic and may be coated with a relatively more flexible thermoset layer 480 to form an airway tube 410. The airway tube 410 may also be coated with more than one flexible thermoset layer 480. Figure 7 shows multiple windows 472 produced in the dorsal face of the skeleton 470 by ribs 474 linking the left side of the skeleton to the right side of the skeleton. Figure 9 shows a skeleton with a single window 472 and no ribs.

Figure 10 shows a method of making an LMA in which first a skeleton 470 is provided and a layer 480 of a relatively more flexible thermoset material is overmoulded onto the skeleton 470 to form an airway tube 410 (see arrow A). In this embodiment, the skeleton 470 comprises a single window 472, a bite block 464 and a tab 466. In the second step (see arrow B), a connector 460 that corresponds in shape and dimension with the internal shape of the proximal end 412 of the airway tube 410, is fitted to the proximal end 412 of the airway tube 410. In this embodiment, the connector 460, for connection of the LMA 400 to a gas supply and drain has major and minor bores 468, 469.

The third step of the method shown in Figure 10 (see arrow C) comprises adding an oesophageal drain tube 458 such that the proximal end of the oesophagal drain tube 458 is attached to the minor bore 469 of the connector 460, the body of the oesophagal drain tube 458 extends through the airway tube 410, and the distal end of the oesophagal drain tube 458 is extends out of the distal end of the airway tube 410.

In the fourth step, a mask body 431 comprising an integral conduit 450 is overmoulded onto the distal end of the airway tube 410 such that the oesophagal drain tube 458 is attached to the conduit 450 (see arrow D). This ensures that the oesophagal drain extends from the drain outlet 454 through the conduit 450 and through the oesophagal drain tube 458 to the minor bore 469.

The fifth step of the method shown in Figure 10 (see arrow E) comprises attaching a cuff 434 to the mask body 431. In this embodiment, the cuff 434 is an inflatable cuff, and so the cuff 434 is formed by blow-moulding prior to attaching it to the mask body 431.